In terms of computational load, the encryption operations are heavy duties occupying significant CPU time, and thus, they are serious power consumers. Reducing this load is especially important in battery-constrained computational environments with limited processing capacities such as the sensor networks, unmanned aerial vehicles, mobile video transmission, and etc.
When data volume is huge such as the case in video transmission, encryption of the whole data introduces a heavy computational load, and also a serious power consumption in parallel. Thus, methods to reduce this load have attained significant attention. There are some developments present in the known state of the art that aim to reduce the amount of encryption operations while securing data. The main approach in those studies is selective (or partial) encryption of the data. In selective encryption some selected parts that are assumed to be important information content of the data are encrypted, and the rest of the data is transmitted/stored in plain format.
The daily practice in securing data is to first compress the data and then encrypt it with an encryption scheme that is assumed to be secure. In that sense perform the compression and encryption steps together has also been considered. However, notice that, in that approach the number of encryption operations are not reduced, but the main point is to achieve the compression and encryption in a single step to gain from elapsed time. We provide some of the exemplary patents regarding to both combined compression and encryption as well as the partial (selective) encryption.
For example in the US2016124983A1 patent document which can be given as an example to these developments, secure compression algorithms are provided that may be employed as a single operation on raw data to produce compressed and encrypted data. In embodiments, the algorithms described herein may be performed using any type of dictionary based encryption. In one embodiment, upon adding a new prefix to a dictionary table, the dictionary table may be permuted to randomize the entries into the table. The randomization may be based upon a permutation value generated by a deterministic pseudo-random generator and/or pseudo-random function. Other embodiments of randomization may be employed to provide secure compression.
In the paper titled “A simple storage scheme for strings achieving entropy bounds” (FERRAGINA et all, Theoretical Computer SCI, Amsterdam, Vol. 372) a non prefix free code where the sequence of code words is separated from the information of the starting position of each code words is disclosed.
In the American Patent document numbered US20120134496 a method of partial encryption wherein a server receiving a sequence of image frames comprises the image frames into blocks of variable size and parameters representing inter frames including block sizes, is disclosed.
In the American Patent document numbered US2007083467A1 within the known state of the art, the invention pertains to improved techniques to partially encrypt media files. The encryption serves to cryptographically secure only a portion of the media data within a media file, while the remaining portion of the media data is not cryptographically secured. Although only partial encryption is used, the portion being encrypted serves to substantially disrupt usefulness of other parts of the media file which are not encrypted. In other words, the partial encryption renders the media file substantially unusable by unauthorized users.
In the American Patent document numbered US2007110225A1 within the known state of the art, methods and devices are provided for accelerating the throughput and or reducing the power consumption of symmetric cryptography algorithms. Certain computations of a symmetric encryption or decryption algorithm are performed during a first phase, the results are saved to memory, and the results are retrieved to encode data during a second phase. If the first phase is implemented while the battery is being charged and the second phase is implemented while the system runs on battery power, the battery life is significantly extended compared to the battery life when all phases are implemented using solely battery power.
In the American Patent document numbered US2004193871A1 within the known state of the art, particular portions of a message receive strong encryption while other parts of the message are less strongly encrypted or even unencrypted, resulting in a differentially encrypted data set. The data set is transmitted to a receiving end where it may be decrypted as desired. Receiving stations requiring the encrypted information and having authorized access may decrypt it, while other stations may decrypt this information only partially or not at all. Required computational power is reduced both on the client side and in channel processing because only selected portions of the message are subject to strong encryption and decryption processing, and latency and problems associated with latency are reduced.
In the American Patent document numbered US2007263876A1 within the known state of the art, methods and devices related to compression and encryption of data. Data to be encrypted and compressed is first received and then stored in physical memory. Once stored in a data structure in physical memory, the data is streamed to a process which compresses the data. The compressed data is then streamed, from the physical memory, to an encryption process. The compressed and encrypted data can then be transmitted. To decrypt and decompress, the compressed and encrypted data is first read into another data structure that stores the data into physical memory. The data is then streamed from the physical memory to, in turn, a decryption process and then a decompression process.
There are lots of patents based on selective (partial) encryption especially targeting the multimedia data transmission and storage also, such as US20050141713A1 Selective multimedia data encryption (SCM microsystems), US US20080065903A1 Selective encryption of data stored on removable media in an automated data storage library (IBM), U.S. Pat. No. 7,039,938B2 Selective Encryption for video-on-demand, U.S. Pat. No. 5,805,700A Policy based selective encryption of compressed video data (Intel), and many more.
It had been previously shown that symetric security algorithms roughly doubles the energy consumption of normal operation in those environments, and asymetric security algorithms increase the energy usage per bit in orders of magnitudes. Providing the data security in such platforms is becoming more and more important considering their wide-spread in the fast approaching era of the internet of things (IoT), where privacy will be a necessity rather than a preference.
As it can be understood from the similar mentioned documents above different methods are being used in order to develop an encryption method to be applied on compressed data. The difference of the proposed study from selective (partial) encryption is that the proposed invention provides the security of the full data, where in selective encryption only the selected sections of the data are secured. The reduction in the amount of encryption improves on larger files with the proposed technique, where around 10 percent encryption of the data becomes sufficient. In selective encryption the ratio is fixed regardless of the size of the data. When compared to combined encryption/compression schemes, those schemes do not aim to reduce the encryption operations but to reduce the time required for the total operations, and thus, not very much related with the aim of this invention.